Making animations that fit avatars

If every avatar is a different shape with different length arms and legs etc then how do you make animations that work properly? For example I made a praying pose that fits myself perfectly but I noticed on others that it doesnt work at all and the hands are in the wrong posiition. I had a look at some shops in SL selling animations and all the animations I tried worked very well on myself. How do you create them so that they work well on everyone??
Im baffled.

It comes down to experience and trial-and-error. There's no technical fix for making animations fit, it's just about designing toward a generic avatar size and setting up the movements so that errors are less noticeable. For example, the amount that the hands are off in a praying pose will vary depending on the angle that the arms are held at.

Yes it can be done. Quite easily.

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I developed this a while back. You can fit a mannequin to an avatars basic shape. what I have have seen people do is create the BHV pose with U-pose then import this reference pose into other programs such as Poser to do more complex animations. So no more guessing.

How do I fit a mannequin to an avatrs basic shape? How does this make any difference when so many avatars are different shapes? What is U-pose?

If is about the size of the avatar u can get that from script and add in variable which depend on avatar's height for example.
I 've creater some animated gallows where every avatar hangs on a rope, but some of them were not fit for it, i had same problem, but i made the script to depend on the avatar's height and it works perfect.
llGetAgentSize(llAvatarOnSitTarget()) - will return you the size of the avatar who sits on the pose ball.